Use either an ohm meter or a powered test light. Put one lead on one end and the other lead on the other end. If the test light lights or the ohm meter shows zero resistance, then its good. If no light or ohm meter shows infinite resistance then its history.

This really is same design as those old type glass tube fuses they used in cars or the paper cartridge fuses in old type house fuse boxes.

You will probably have to go to a contractors electrical supply store if you don't have a very, very good local hardware store for a replacement. They will be able to test and to tell you the amperage of the fuse. A special order would not be unexpected.

An ohmeter would be the most straight forward way to test the fuse. You could rig up a test light and check for continuity through the fuse though.

As far as finding one (quantity one), your best bet might be an appliance store with a service/parts department.

When I worked at the electical wholesale house years ago, we didn't stock Bussman type SC fuses (pretty much an appliance item). I could have ordered them. If you were willing to wait a week or two until I placed my regular Bussman order, I could have ordered them with no inbound freight (UPS in this case), but you would have had to buy a standard package quantity (probably 5 or 10 fuses). I could have ordered one for you from a larger branch of our company, but you would have had to pay inbound freight from that branch which I'm sure would cost several times as much as the fuse.

I'm not sure from the pic but if this is the same size as a regular "old fashioned car fuse" but made from white ceramic IIRC a few years back Radio Shack stocked them a few years back. Haven't checked recently though. I think the ceramic is necessary due to "internal radiation"; glass fuse won't hold up so never tried one.